Nanocomposites are polymer systems containing inorganic particles with at least one dimension in the nanometer range. Some examples of these are disclosed in U.S. Pat. Nos. 6,060,549, 6,103,817, 6,034,164, 5,973,053, 5,936,023, 5,883,173, 5,807,629, 5,665,183, 5,576,373, and 5,576,372. Common types of inorganic particles used in nanocomposites are phyllosilicates, an inorganic substance from the general class of so called “nano-clays” or “clays.” Ideally, intercalation should take place in the nanocomposite, wherein the polymer inserts into the space or gallery between the clay surfaces. Ultimately, it is desirable to have exfoliation, wherein the polymer is fully dispersed with the individual nanometer-size clay platelets. Due to the general enhancement in air barrier qualities of various polymer blends when clays are present, there is a desire for a nanocomposite with low air permeability; especially a dynamically vulcanized elastomer nanocomposite such as used in the manufacture of tires.
The preparation of nanocomposites uses a number of methods to generate exfoliated clays. One of the most common methods relies upon the use of organically modified montmorillonite clays. Organoclays are typically produced through solution based ion-exchange reactions that replace sodium ions that exist on the surface of sodium montmorillonite with organic molecules such as alkyl or aryl ammonium compounds and typically known in the industry as swelling or exfoliating agents. See, e.g., U.S. Pat. No. 5,807,629, WO 02/100935, and WO 02/100936. Other background references include U.S. Pat. No. 5,576,373, U.S. Pat. No. 5,665,183, U.S. Pat. No. 5,807,629, U.S. Pat. No. 5,936,023, U.S. Pat. No. 6,121,361, WO 94/22680, WO 01/85831, and WO 04/058874.
One method to improve the organoclay performance is to use functionalized polymers to treat the clay. This approach uses materials that are soluble in water or materials that can be incorporated into the polymerization reaction. This approach has been used to prepare nylon nanocomposites, using for example, oligomeric and monomeric caprolactam as the modifier. Polyolefin nanocomposites, such as polypropylene nanocomposites, have utilized maleic anhydride grafted polypropylenes to achieve some success in the formation of nanocomposites.
For example, it is known to utilize exfoliated-clay filled nylon as a high impact plastic matrix, such as disclosed in U.S. Pat. No. 6,060,549 to Li et al. In particular, Li et al. disclose a blend of a thermoplastic resin such as nylon and a copolymer of a C4 to C7 isoolefin and a para-methylstyrene and a para-(halomethylstyrene), the blend also including nylon-containing exfoliated clays that are used as a high impact material. Further, Japanese Unexamined Application P2000-160024 by Yuichi et al. discloses a thermoplastic elastomer composition which can be used as an air barrier, including a blend similar to that disclosed in Li et al.
Elastomeric nanocomposite innerliners and innertubes have also been formed using a complexing agent and a rubber, where the agent is a reactive rubber having positively charged groups and a layered silicate uniformly dispersed therein. See, for example, Kresge et al. U.S. Pat. No. 5,665,183 and U.S. Pat. No. 5,576,373. This approach uses pre-formed positively charged reactive rubber components.
Nanocomposites have also been formed using non-ionic, brominated copolymers of isobutylene and para-methylstyrene, and blends of these copolymers with other polymers. See, for example, Elspass et al. U.S. Pat. No. 5,807,629 and U.S. Pat. No. 6,034,164.
The isobutylene-p-methylstyrene copolymers, a variety of functionalized derivatives thereof, and BIMSM in particular, are useful in various processes for making clay nanocomposites. See, for example, U.S. application Ser. No. 11/183,361, Split-Stream Process for Making Nanocomposites, by W. Weng et al., filed Jul. 18, 2005; and U.S. application Ser. No. 11/184,000, Functionalized Isobutylene Polymer-Inorganic Clay Nanocomposites and Organic-Aqueous Emulsion Process, by W. Weng et al., filed Jul. 18, 2005.
There still exists a need to improve exfoliation of the clay, processability of the nanocomposites, and final product properties.